Audiophile Products Tube Head Pre Amp in a Miniature Package Tube Buffer: 1 X 5670 (2C51) vacuum tube. DC amp uses no coupling capacitors Frequency Response: 6Hz~100Khz ,-1dB at 600 ohms loading, low noise Power Input: 110V / 220V Switchable Inputs 2 X RCA and Outputs 1 X RCA Size: Size: 11cm/4.3in(L) x 8cm/3.2in(W) x 10cm/4.0in(H)